Re: Blockbusting news, results get worse

Pavel Machek
2003-10-29T20:02:04Z

Hi!

> > >> or put it under heavy write workload and remove
> > >> power.
> > >>
> > > Can you tell us more about what really happens to disk drives when the
> > > power is cut while a block is being written? We engage in a lot of
> > > uninformed speculation, and it would be nice if someone who really knows
> > > told us....
> > >
> > > Do drives have enough capacitance under normal conditions to finish
> > > writing the block? Does ECC on the drive detect that the block was bad
> > > and so we don't need to detect it in the FS?
> >
> >
> > Does it really matter to speculate about this?
> >
> > If you don't FLUSH CACHE, you have no guarantees your data is on the
> > platter.
>
> I think that the idea that is floating around is to deliberately ruin
> the formatting on part of the drive in order to simulate a bad block.
>
> Operation of disk drives immediately after a power failiure has been
> discussed before, by the way:
>
> http://marc.theaimsgroup.com/?l=linux-kernel&m=100665153518652&w=2

Well, that looks like pure speculation.

BTW I *do* believe that powerfail can make the sector bad. Imagine you
bump into bad sector during write, and need to reallocate...

Pavel
--
When do you have a heart between your knees?
[Johanka's followup: and *two* hearts?]